MICROANATOMY

Detailed explanation-1: -Two capsules completely cover the thyroid gland. The true capsule is made up of fibro-elastic connective tissue. The false capsule comprises the pre-tracheal layer of the deep cervical fascia. It consists of deep capillary plexus deep to the true capsule.

Detailed explanation-2: -Thyroid follicles are spheroidal structures of different sizes, formed by a single layer of epithelial cells, the follicular cells.

Detailed explanation-3: -Thyroxine (T4) is the main secretory product of the thyroid follicle cells and is converted to the active hormone, triiodothyronine (T3), in the tissues under the influence of microsomal deiodinase enzymes, which remove the iodine from the “outer” ring (5’-deiodination).

Detailed explanation-4: -Thyroid follicular cells (also called thyroid epithelial cells or thyrocytes) are the major cell type in the thyroid gland, and are responsible for the production and secretion of the thyroid hormones thyroxine (T4) and triiodothyronine (T3).